The 1968 Tokachi-Oki earthquake (May 6, 1968) damaged the haobrur structures in the southern part of Hokkaido and the Pacific coast of Tohoku-area, the northen part of Honshu.
　In this Report, we investigated the stability of these harbour structures applying the present design methods.
　Based on the results of this analysis, we noted the problems on the method of design to be solved.
　Adding this the analysis of damage caused by Hyuga-Nada earthquake (April 1,1968) is showed in this report.